To determine the effect of ketamine, compared to propofol, when used an an anesthetic agent for electroconvulsive therapy (ECT) in the treatment of major depressive disorder (MDD). We hypothesize that ketamine, compared to propofol, will improve the the symptoms of MDD when used as the anesthetic agent to facilitate ECT. Additionally, we hypothesize the dissociative and cardiovascular effects of ketamine will be minimal.